The control mechanism of the present invention finds particular application in a telephone answering machine which utilizes a first cassette-type tape unit on which an announcement message is recorded for transmission to a calling party during an itital time interval (T.sub.1) upon the receipt of a ring signal; and which utilizes a second cassette-type tape unit for receiving messages from a calling party during a subsequent message recording interval (T.sub.2). For each cassette, a record/playback head is mounted on a sliding plate together with a pinch roller, and for normal forward playback/record operation the plate is moved into its operative position such that the pinch roller presses the tape of the corresponding cassette against a motor driven capstan to cause the tape to be drawn from the supply reel to the take-up reel of the cassette; and such that the corresponding record/playback head is moved to a position adjacent to the tape in magnetically coupled relationship with the tape. In addition, when the sliding plate is moved into its operative position, a gear train couples the motor driven capstan to the take-up reel to rotate the take-up reel to enable it to wind up the tape.
For rewind operation, the sliding plate is released and is spring-biased to its standby position to move the record/playback head back from the tape and the pinch roller back from the capstan, and also to disengage the take-up reel from the capstan. At the same time, a further gear train couples the rewind reel of the cassette to the drive motor to cause the rewind reel to rotate in the opposite direction and rewind the tape.
It is usual in the prior art machines to provide an appropriate high-power electromagnetic solenoid in conjunction with each cassette to draw the corresponding sliding plate forward to its operational position against the bias of a return spring. It is also usual to provide a second electromagnetic solenoid in conjunction with each cassette to couple the drive motor to the rewind reel for the rewind operation. However, the electromagnetic solenoids used in the prior art apparatus of necessity are relatively large and expensive, and they draw relatively large electric currents, since it is necessary for each solenoid to exert a relatively large force on the controlled components in order to accomplish their desired purpose.
A control mechanism is described in U.S. Pat. No. 4,189,079 for use in a cassette-type telephone answering machine, in which the force for driving the sliding plate forward to its operational position against its spring bias, and the force for coupling the motor driven capstan to the rewind spindle of the capstan for the rewind operation, are provided by the main drive motor of the machine, rather than by high power electromagnetic solenoids. Relatively small, low power electromagnets are provided for latching and unlatching the mechanism which couples the drive motor to the sliding plate.
The mechanism of the present invention is of the same general type as described in U.S. Pat. No. 4,189,079. However, the mechanism of the present invention utilizes a different type of mechanical coupling between the motor and the sliding plate having a more positive action than the mechanism described in the patent.